1. Field of the Invention
This invention relates to a process for producing a developer used for making visible electrostatic latent images in electrophotography, electrostatic recording, electrostatic printing, and the like, and more particularly, to a process for producing a liquid developer containing a toner having a negative charge.
2. Description of the Prior Art
Developers used for making electrostatic latent images visible are conventionally roughly classified as dry developers and wet developers from the standpoint of the form of the developer. In dry developers, coloring agents, such as carbon black, in finely divided form are used as toners, and known development methods using dry developers include the cascade method, the magnetic brush method, the powder cloud method, and the like.
On the other hand, wet developers include a pigment kneaded in an electrically insulating carrier liquid, a dye which has been chemically reacted with a dispersing resin and then dispersed in a carrier liquid, and the like. However, the use of pigments has the disadvantages that the color tone is restricted, and the resin combined is also restricted from the standpoint of electrical charge and dispersibility. Moreover, in using polymeric coloring materials in which the dye is chemically bonded to the polymer, technical skill in the synthesis, e.g., in the introduction of functional groups for the chemical bonding, is required. In addition, many proposals have been made so far for wet developers containing a toner having a negative charge, but they involve many problems that the electrical charge is unstable on long-time storage or on repeated use, the stability of the dispersion is poor, or the like.